PIK3CA and neuroendocrine carcinoma: Although the frequencies of TP53 and APC mutations in the NEC group were slightly higher than those in the AC group (43% vs. 35%; p = 0.0546, 37% vs. 31%; p = 0.6569, respectively), PIK3CA mutations were less frequently identified in the NEC group (10% vs. 15%; p = 0.7633).